In the prior art linear bearing, round balls are used to rotatably bear the retaining portion and movable portion of the bear. However, all the Prior arts about linear bearings have complicated structure and higher cost. Furthermore the maintenance and lubrication works are difficult. When any rolling ball is worn or deformed, it will affect the liner motion. Furthermore ratio of malfunction is increased with the number of the rolling balls. Therefore, the lifetime of the linear bearing is short. When any rolling ball is destroyed, it is difficult to repair. As a result, a whole linear bearing is updated, but it is waste and uneconomic.
Therefore, inventor of the present invention is aimed to improve the above mentioned defects about the linear bearing to have a simple structure and to be low cost, can be easily maintained and lubricated.